Sub-nanosecond laser cataract surgery system

ABSTRACT

Systems and methods for fragmenting a lens by a laser cataract surgery system includes a sub-nanosecond laser source generating a treatment beam that includes a plurality of laser beam pulses. An optical delivery system is coupled to the sub-nanosecond laser source to receive and direct the treatment beam. A processor is coupled to the sub-nanosecond laser source and the optical delivery system. The processor includes a tangible non-volatile computer readable medium comprising instructions to determine a lens cut pattern for lens fragmentation and determine a plurality of energies of the treatment beam as a linear function of a depth of the lens cut pattern. The treatment beam is output according to the lens cut pattern and the determined energies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional application and claims the benefitunder 35 U.S.C. § 119(e) of U.S. Provisional Application Ser. No.62/187,771, filed Jul. 1, 2015, which is incorporated herein in itsentirety by reference.

BACKGROUND

The present disclosure relates generally to tissue cutting induced by apulsed laser beam and the energy of the pulsed laser beam. Althoughspecific reference is made to cutting tissue for surgery such ascataract surgery, embodiments as described herein can be used in manyways with many materials to treat one or more of many materials, such ascutting of optically transparent materials.

Cutting of materials can be done mechanically with chisels, knives,scalpels and other tools such as surgical tools. Pulsed lasers can beused to cut one or more of many materials and have been used for lasersurgery to cut tissue. However, prior methods and apparatus of cuttingcan be less than desirable in at least some instances. For example, atleast some prior methods and apparatus for cutting materials such astissue are unsuitable due to their cost and size.

Cataract extraction is one of the most commonly performed surgicalprocedures in the world. A cataract is formed by opacification of thecrystalline lens or its envelope (the lens capsule) of the eye. Thecataract obstructs passage of light through the lens. A cataract canvary in degree from slight to complete opacity. Early in the developmentof an age-related cataract the power of the lens may be increased,causing near-sightedness (myopia). Gradual yellowing and opacificationof the lens may reduce the perception of blue colors as thosewavelengths are absorbed and scattered within the crystalline lens.Cataract formation typically progresses slowly resulting in progressivevision loss. Cataracts are potentially blinding if untreated.

A common cataract treatment involves replacing the opaque crystallinelens with an artificial intraocular lens (IOL). Presently, an estimated15 million cataract surgeries per year are performed worldwide. Thecataract treatment market is composed of various segments includingintraocular lenses for implantation, viscoelastic polymers to facilitatesurgical procedures, and disposable instrumentation including ultrasonicphacoemulsification tips, tubing, various knives, and forceps.

Presently, cataract surgery is typically performed using a techniquetermed phacoemulsification in which an ultrasonic tip with associatedirrigation and aspiration ports is used to sculpt the relatively hardnucleus of the lens to facilitate removal through an opening made in theanterior lens capsule. The nucleus of the lens is contained within anouter membrane of the lens that is referred to as the lens capsule.Access to the lens nucleus can be provided by performing an anteriorcapsulotomy in which a small (often round) hole is formed in theanterior side of the lens capsule through which the surgeon excises thewhole lens. Access to the lens can also be provided by performing amanual continuous curvilinear capsulorhexis (CCC) procedure. The lensmay then be fragmented by segmenting and/or softening the lens by afemtosecond laser to aid in removal by a phacoemulsification tip.Removal of the lens with the phacoemulsification tip is then performedthrough a primary corneal incision, for instance. After removal of thelens nucleus, a synthetic foldable intraocular lens (IOL) can beinserted into the remaining lens capsule of the eye.

Prior methods and apparatuses to incise tissue with laser beams can beless than ideal in at least some instances. For example, femtosecondlaser cutting systems are used in performing lens fragmentation.Femtosecond laser technology provides a short duration (e.g.,approximately 10⁻¹³ seconds in duration) laser pulse (with energy levelin the micro joule range) that can be delivered to a tightly focusedpoint to disrupt tissue. Femtosecond lasers are well-suited forproviding clean cuts in a lens through a relatively wide range of energylevels. However, the high cost and large size of femtosecond lasercutting systems prevent those systems from more widespread usage.

Infrared laser cutting systems, such as picosecond lasers, are smallerand more cost-effective relative to femtosecond laser cutting systems,but are not used for lens fragmentation. These systems provide cuts to anucleus of the lens with energy level in the tens of micro joule rangethat are coarser than the cuts provided by a femtosecond laser beam. Thequality of the cuts are poor and non-uniform throughout the lens,resulting in defects such as patching, incomplete cuts and excess damagefrom large bubbles generated by the laser. Examples of incompletecutting includes bridging where two cut portions remain connectedtogether, thereby complicating subsequent nucleus removal. Excess damageto the tissue creates lamella separation that crack the lens and blocksubsequent laser pulses. Therefore, further laser cutting is notpossible once a lens is delaminated. Although infrared laser systems areattractive from a cost perspective, these performance deficiencies haveprevented their use for lens fragmentation.

Thus, improved methods and systems for lens fragmentation and treatingcataracts are needed. In light of the above, it would be desirable tohave improved methods and apparatus of treating materials with laserbeams, such as the surgical cutting of tissue to treat cataracts withcost effective surgical systems. At least some of the above deficienciesof the prior methods and apparatus are overcome by the embodimentsdescribed herein.

SUMMARY

Improved laser eye surgery systems, and related methods, are provided.The laser eye surgery systems use a laser to form precise incisions inthe crystalline lens nucleus. Although specific reference is made totissue cutting for laser eye surgery, embodiments as described hereincan be used in one or more of many ways with many surgical proceduresand devices, such as orthopedic surgery, robotic surgery andmicrokeratomes.

Thus, in one aspect, a laser cataract surgery system is provided and mayinclude a sub-nanosecond laser source generating a treatment beam thatincludes a plurality of laser beam pulses. An optical delivery systemmay be coupled to the sub-nanosecond laser source to receive and directthe treatment beam. A processor may be coupled to the sub-nanosecondlaser source and the optical delivery system. The processor includes atangible non-volatile computer readable medium including instructions todetermine a lens cut pattern for lens fragmentation and determine aplurality of energies of the treatment beam as a linear function of adepth of the lens cut pattern. The treatment beam may be outputaccording to the lens cut pattern and the determined energies.

In some embodiments, the plurality of energies of the treatment beam maybe between twice an energy threshold and ten times an energy threshold.The energy threshold is an energy level at which visible damage intissue is first observed. In some variations, the sub-nanosecond lasersource generates the treatment beam with an energy five times the energythreshold of the tissue. The sub-nanosecond laser source may be apicosecond laser. The sub-nanosecond laser may generate a 150 picosecondtreatment beam.

In some variations, the laser system may include an image capture systemfor capturing an image of the eye. A patient interface system may couplethe eye with the optical delivery system so as to constrain the eyerelative to the optical delivery system.

In some embodiments, a method of fragmenting a lens is provided andincludes the steps of determining a lens cut pattern for lensfragmentation. A treatment beam may be generated that includes aplurality of laser beam pulses by a sub-nanosecond laser source. Aplurality of energies of the treatment beam may be determined as alinear function of a depth of the lens cut pattern. The treatment beammay be output according to the lens cut pattern and the determinedenergies.

In some variations, the plurality of energies of the treatment beam arebetween twice an energy threshold and ten times an energy threshold. Theenergy threshold may be an energy level at which visible damage intissue is first observed. The sub-nanosecond laser source may generatethe treatment beam with an energy five times the energy threshold of thetissue. The sub-nanosecond laser source may be a picosecond laser. Thesub-nanosecond laser may generate a 150 picosecond treatment beam.

In other variations, an image of the eye may be captured by an imagecapture system. The eye may be coupled with the optical delivery systemso as to constrain the eye relative to the optical delivery system by apatient interface system.

Variations of the laser eye surgery system are provided. For example, alaser cataract surgery system includes a sub-nanosecond laser sourcegenerating a treatment beam that includes a plurality of laser beampulses. An optical delivery system may be coupled to the sub-nanosecondlaser source to receive and direct the treatment beam. A processor maybe coupled to the sub-nanosecond laser source and the optical deliverysystem. The processor may include a tangible non-volatile computerreadable medium including instructions to determine a lens cut patternfrom a posterior to an anterior of the lens for lens fragmentation. Aplurality of energies of the treatment beam may be scaled as a functionof a depth of the lens cut pattern to maintain a bubble volume formed bythe single pulse of treatment beam. The treatment beam may be outputaccording to the lens cut pattern and the determined energies.

In some variations, the plurality of energies may be scaled linearlywith a depth of the lens cut pattern. The energy of the treatment beammay decrease as a function of the depth of the lens linearly from theposterior to the anterior of the lens. The energy of the treatment beamat the posterior of the lens may be between twice an energy thresholdand ten times an energy threshold. The energy threshold may be an energylevel at which visible damage in tissue is first observed.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIG. 1 is a schematic diagram of a laser surgery system, in accordancewith many embodiments;

FIG. 2 is a schematic diagram of the laser surgery system of FIG. 1, inaccordance with many embodiments;

FIG. 3 is a graph illustrating penetration depth versus energy in a lenscut, in accordance with many embodiments;

FIG. 4 is a graph illustrating bubble volume versus cut depth in a lenscut, in accordance with many embodiments;

FIG. 5 shows a flowchart of a fragmentation pattern method of a lens, inaccordance with many embodiments.

DETAILED DESCRIPTION

Methods and systems related to laser eye surgery are disclosed. A laseris used to form precise incisions in the cornea, in the lens capsule,and/or in the crystalline lens nucleus. In many embodiments, a laser eyesurgery system includes a laser source to produce a laser pulsetreatment beam to incise tissue within the eye, an imaging system tomeasure the spatial disposition of external and internal structures ofthe eye in which incisions can be formed, a scanning assembly operableto scan the treatment beam, and can include a video subsystem that canbe used to, for example, provide images of the eye during docking of theeye to the laser eye surgery system and also provide images of the eyeonce the docking process is complete. In many embodiments, a liquidinterface is used between a patient interface lens and the eye. The useof the liquid interface avoids imparting undesirable forces to thepatient's eye.

The embodiments as described herein are particularly well suited fortreating tissue, such as with the surgical treatment of tissue. In manyembodiments, the tissue comprises an optically transmissive tissue, suchas tissue of an eye. The embodiments as described herein can beparticularly well suited for increasing the quality of the cutting ofthe material such as tissue, for example.

As used herein, like characters such as reference numerals and lettersdescribe like elements. As used herein, the terms anterior and posteriorrefers to known orientations with respect to the patient. An energythreshold is used herein to mean an energy level of laser beam pulsesthat cause the first visible damage in tissue. Photodisruption isgenerally used for the first visible damage in tissue by a UV laser.

Depending on the orientation of the patient for surgery, the termsanterior and posterior may be similar to the terms upper and lower,respectively, such as when the patient is placed in a supine position ona bed. The terms distal and anterior may refer to an orientation of astructure from the perspective of the user, such that the terms proximaland distal may be similar to the terms anterior and posterior whenreferring to a structure placed on the eye, for example. A person ofordinary skill in the art will recognize many variations of theorientation of the methods and apparatus as described herein, and theterms anterior, posterior, proximal, distal, upper, and lower are usedmerely by way of example.

FIG. 1 schematically illustrates a laser surgery system 10, according tomany embodiments. The laser surgery system 10 may include a lasersource/assembly 12, a confocal detection assembly 14, a free-floatingmechanism 16, a scanning assembly 18, an objective lens assembly 20, anda patient interface device 22. The patient interface device 22 may beconfigured to interface with a patient 24. The patient interface device22 may be supported by the objective lens assembly 20, which may besupported by the scanning assembly 18, which may be supported by thefree-floating mechanism 16. The free-floating mechanism 16 may have aportion having a fixed position and orientation relative to the laserassembly 12 and the confocal detection assembly 14. An optical deliverysystem for receiving and directing the treatment beam may comprise someor all of the components coupled to the to the sub-nanosecond laserassembly 12.

In some embodiments, the patient interface device 22 can be configuredto be coupled to an eye of the patient 24 using vacuum as described inco-pending U.S. patent application Ser. No. 14/068,994, entitled “LiquidOptical Interface for Laser Eye Surgery System,” filed Oct. 31, 2013,the entire disclosure of which is incorporated herein by reference. Thelaser surgery system 10 can further optionally include a base assembly26 that can be fixed in place or be repositionable. For example, thebase assembly 26 can be supported by a support linkage that isconfigured to allow selective repositioning of the base assembly 26relative to a patient and/or securing the base assembly 26 in a selectedfixed position relative to the patient. Such a support linkage can be afixed support base or a movable cart that can be repositioned to asuitable location adjacent to a patient. In many embodiments, thesupport linkage includes setup joints with each setup joint beingconfigured to permit selective articulation of the setup joint, and canbe selectively locked to prevent inadvertent articulation of the setupjoint, thereby securing the base assembly 26 in a selected fixedposition relative to the patient when the setup joints are locked.

In many embodiments, the laser assembly 12 may be configured to emit anelectromagnetic radiation beam 28. The beam 28 can include a series oflaser pulses of any suitable energy level, duration, and repetitionrate. In many embodiments, the laser assembly 12 incorporatessub-nanosecond laser technology where a short duration (e.g.,approximately 10 ns to 1 picosecond in duration) laser pulse (withenergy level in the tens of micro joules range) can be delivered to atightly focused point to disrupt tissue, thereby substantially loweringthe energy level required to image and/or modify an intraocular targetas compared to laser pulses having longer durations. The laser assembly12 may produce laser pulses having a wavelength suitable to treat and/orimage tissue. For example, the laser assembly 12 can be configured toemit an electromagnetic radiation beam 28 such as that emitted by any ofthe laser surgery systems described in co-pending U.S. patentapplication Ser. No. 14/069,044, entitled “Laser Eye Surgery System,”filed Oct. 31, 2013, and U.S. patent application Ser. No. 12/987,069,entitled “Method and System For Modifying Eye Tissue and IntraocularLenses,” filed Jan. 7, 2011, the full disclosures of which areincorporated herein by reference.

In some embodiments, the laser assembly may produce laser pulses havinga wavelength of 355 nm with a numerical aperture NA in the range of 0.05to 0.40, and preferably 0.15. The pulse length may be 0.6 ns with apulse rate of 1 kHz to 1 mHz, and preferably 70 kHz to 100 kHz. Spotspacing may be from 6 μm to 40 μm.

The selection of NA may be based upon laser power, pulse rate, cut time,as well as safe incidental exposure levels of the iris and other oculartissues not targeted by the cut. For instance, as the NA decreases, thelaser power required increases. Also, the time needed for a cut of unitarea (mm²) increases with increasing NA due to lower threshold energies.Therefore, increased NA tends to lead to an increased number of pulsesand longer cut times.

In other varying embodiments, the laser assembly 12 may produce laserpulses having a wavelength between 800 nm to 1200 nm, and preferablybetween 1020 nm to 1050 nm. The pulse duration of the laser light canvary from 1 ps to 1000 ps. The pulse repetition frequency can also varyfrom 10 kHz to 500 kHz. Safety limits with regard to unintended damageto non-targeted tissue bound the upper limit with regard to repetitionrate and pulse energy. Threshold energy, time to complete the procedure,and stability can bound the lower limit for pulse energy and repetitionrate. The peak power of the focused spot in the eye 24 and specificallywithin the crystalline lens and the lens capsule of the eye issufficient to produce optical breakdown and initiate visible damage intissue. In yet another embodiment, the laser assembly 12 may have adiode-pumped solid-state configuration with a 1030 (+/−5) nm centerwavelength. The laser assembly 12 can also include two or more lasers ofany suitable configuration.

The laser assembly 12 may include control and conditioning components.In an embodiment, the control components may include a beam attenuatorto control the energy of the laser pulse and the average power of thepulse train, a fixed aperture to control the cross-sectional spatialextent of the beam containing the laser pulses, one or more powermonitors to monitor the flux and repetition rate of the beam train andtherefore the energy of the laser pulses, and a shutter to allow/blocktransmission of the laser pulses. The conditioning components mayinclude an adjustable zoom assembly and a fixed optical relay totransfer the laser pulses over a distance while accommodating laserpulse beam positional and/or directional variability, thereby providingincreased tolerance for component variation.

In many embodiments, the laser assembly 12 and the confocal detectionassembly 14 may have fixed positions relative to the base assembly 26.The beam 28 emitted by the laser assembly 12 may propagate along a fixedoptical path through the confocal detection assembly 14 to thefree-floating mechanism 16. The beam 28 may propagate through thefree-floating mechanism 16 along a variable optical path 30, which maydeliver the beam 28 to the scanning assembly 18. In many embodiments,the beam 28 emitted by the laser assembly 12 may be collimated so thatthe beam 28 is not impacted by patient movement-induced changes in thelength of the optical path between the laser assembly 12 and the scanner18. The scanning assembly 18 may be operable to scan the beam 28 (e.g.,via controlled variable deflection of the beam 28) in at least onedimension. In many embodiments, the scanning assembly 18 is operable toscan the beam 28 in two dimensions transverse to the direction ofpropagation of the beam 28 and may be further operable to scan thelocation of a focal point of the beam 28 in the direction of propagationof the beam 28. The scanned beam may be emitted from the scanningassembly 18 to propagate through the objective lens assembly 20, throughthe interface device 22, and to the patient 24.

The free-floating mechanism 16 may be configured to accommodate a rangeof movement of the patient 24 relative to the laser assembly 12 and theconfocal detection assembly 14 in one or more directions whilemaintaining alignment of the beam 28 emitted by the scanning assembly 18with the patient 24. For example, the free-floating mechanism 16 may beconfigured to accommodate a range movement of the patient 24 in anydirection defined by any combination of unit orthogonal directions (X,Y, and Z).

In some embodiments, the scanning assembly 18 can include a Z-scandevice and an XY-scan device. The laser surgery system 10 may beconfigured to focus the electromagnetic radiation beam 28 to a focalpoint that is scanned in three dimensions. The Z-scan device may beoperable to vary the location of the focal point in the direction ofpropagation of the beam 28. The XY-scan device may be operable to scanthe location of the focal point in two dimensions transverse to thedirection of propagation of the beam 28. Accordingly, the combination ofthe Z-scan device and the XY-scan device can be operated to controllablyscan the focal point of the beam in three dimensions, including: withina tissue, e.g., eye tissue, of the patient 24. The scanning assembly 18may be supported by the free-floating mechanism 16, which mayaccommodate patient movement, induced movement of the scanning assembly18 relative to the laser assembly 12 and the confocal detection assembly14 in three dimensions.

Because the patient interface device 22 may be interfaced with thepatient 24, movement of the patient 24 may result in correspondingmovement of the patient interface device 22, the objective lens assembly20, and the scanning assembly 18. The free-floating mechanism 16 caninclude, for example, any suitable combination of a linkage thataccommodates relative movement between the scanning assembly 18 and, forexample, the confocal detection assembly 14, and optical componentssuitably coupled to the linkage so as to form the variable optical path30. In an embodiment, the free-floating mechanism 16 can be configuredas described in U.S. patent application Ser. No. 14/191,095 and PCTApplication No. PCT/US2014/018752, filed Feb. 26, 2014 and entitled“Laser Surgery System,” the entire disclosures of which are incorporatedherein by reference.

A portion of electromagnetic radiation beam 28 may reflect from an eyetissue at the focal point and may propagate back to the confocaldetection assembly 14. Specifically, a reflected portion of theelectromagnetic radiation beam 28 may travel back through the patientinterface device 22, back through the objective lens assembly 20, backthrough (and de-scanned by) the scanning assembly 18, back through thefree-floating mechanism 16 (along the variable optical path 30), and tothe confocal detection assembly 14. In many embodiments, the reflectedportion of the electromagnetic radiation beam that travels back to theconfocal detection assembly 14 may be directed to be incident upon asensor that generates an intensity signal indicative of intensity of theincident portion of the electromagnetic radiation beam. The intensitysignal, coupled with associated scanning of the focal point within theeye, can be processed in conjunction with the parameters of the scanningto, for example, image/locate structures of the eye, such as theanterior surface of the cornea, the posterior surface of the cornea, theiris, the anterior surface of the lens capsule, the posterior surface ofthe lens capsule, and so on. In many embodiments, the amount of thereflected electromagnetic radiation beam that travels to the confocaldetection assembly 14 may be substantially independent of expectedvariations in the length of the variable optical path 30 due to patientmovement, thereby enabling the ability to ignore patient movements whenprocessing the intensity signal to image/locate structures of the eye.

The confocal detection assembly 14 may comprise a confocal imagingsystem which operates at the same wavelength as the electromagneticradiation beam. The confocal imaging system combined with an inexpensivesub-nanosecond laser provides a cost effective and compact surgicalsystem.

In many embodiments, the system 10 includes external communicationconnections. For example, the system 10 can include a network connection(e.g., an RJ45 network connection) for connecting the system 10 to anetwork. The network connection can be used to enable network printingof treatment reports, remote access to view system performance logs, andremote access to perform system diagnostics. The system 10 can include avideo output port (e.g., HDMI) that can be used to output video oftreatments performed by the system 10. The output video can be displayedon an external monitor for, for example, viewing and/or training. Theoutput video can also be recorded for, for example, archival purposes.The system 10 can include one or more data output ports (e.g., USB) to,for example, enable export of treatment reports to a data storagedevice. The treatments reports stored on the data storage device canthen be accessed at a later time for any suitable purpose such as, forexample, printing from an external computer in the case where the userwithout access to network based printing.

FIG. 2 schematically illustrates details of an embodiment of the lasersurgery system 10. Specifically, example configurations areschematically illustrated for the laser assembly 12, the confocaldetection assembly 14, and the scanning assembly 18. As shown in theillustrated embodiment, the laser assembly 12 may include an IR laser32, alignment mirrors 34, 36, a beam expander 38, a one-half wave plate40, a polarizer and beam dump device 42, output pickoffs and monitors44, and a system-controlled shutter 46. The electromagnetic radiationbeam 28 output by the laser 32 may be deflected by the alignment mirrors34, 36. In many embodiments, the alignment mirrors 34, 36 may beadjustable in position and/or orientation so as to provide the abilityto align the beam 28 with the downstream optical path through thedownstream optical components. Next, the beam 28 may pass through thebeam expander 38, which can increase the diameter of the beam 28. Theexpanded beam 28 may then pass through the one-half wave plate 40 beforepassing through the polarizer 42. The beam exiting the polarizer 42 maybe linearly polarized. The one-half wave plate 40 can rotate thispolarization. The amount of light passing through the polarizer 42depends on the angle of the rotation of the linear polarization.Therefore, the one-half wave plate 40 with the polarizer 42 may act asan attenuator of the beam 28. The light rejected from this attenuationmay be directed into the beam dump. Next, the attenuated beam 28 maypass through the output pickoffs and monitors 44 and then through thesystem-controlled shutter 46. By locating the system-controlled shutter46 downstream of the output pickoffs and monitors 44, the power of thebeam 28 can be checked before opening the system-controlled shutter 46.

The system 10 can be set to locate the anterior and posterior surfacesof the lens capsule and cornea and ensure that the laser pulse beam 28will be focused on the lens capsule and cornea at all points of thedesired opening. In the embodiment of FIGS. 1 and 2, a confocaldetection assembly 14 is described, although other modalities are withinthe scope of the present invention. Imaging modalities and techniquesdescribed herein, such as for example, Optical Coherence Tomography(OCT), Purkinje imaging, Scheimpflug imaging, structured lightillumination, confocal backreflectance imaging, fluorescence imaging, orultrasound may be used to determine the location and measure thethickness of the lens and lens capsule to provide greater precision tothe laser focusing methods, including 2D and 3D patterning, or otherknown ophthalmic or medical imaging modalities and/or combinationsthereof. An OCT scan of the eye will provide information about the axiallocation of the anterior and posterior lens capsule, the boundaries ofthe cataract nucleus, as well as the depth of the anterior chamber. Thisinformation is then be loaded into the control electronics 70, and usedto program and control the subsequent laser-assisted surgical procedure.The information may also be used to determine a wide variety ofparameters related to the procedure such as, for example, the upper andlower axial limits of the focal planes used for modifying the lenscapsule, cornea, and synthetic intraocular lens implant, among others.

For instance, an optical coherence tomography (OCT) system may be usedin place of the confocal imaging system. The OCT system is configured toproduce a source beam used to locate one or more structures of the eye,such as by measuring the spatial disposition of eye structures in threedimensions. The measured eye structures can include the anterior andposterior surfaces of the cornea, the anterior and posterior portions ofthe lens capsule, the iris, and the limbus. As a non-limiting example,the system 10 can be configured to use an OCT imaging system employingwavelengths from 780 nm to 970 nm, or more particularly, from 810 nm to850 nm. Such an OCT imaging system can employ a reference path lengththat is adjustable to adjust the effective depth in the eye of the OCTmeasurement, thereby allowing the measurement of system componentsincluding features of the patient interface that lie anterior to thecornea of the eye and structures of the eye that range in depth from theanterior surface of the cornea to the posterior portion of the lenscapsule and beyond.

As shown in the illustrated embodiment, the scanning assembly 18 mayinclude a Z-scan device 58 and an XY-scan device 60. The Z-scan device58 may be operable to vary a convergence/divergence angle of the beam 28and thereby change a location of the focal point in the direction ofpropagation of the beam 28. For example, the Z-scan device 58 mayinclude one or more lenses that are controllably movable in thedirection of propagation of the beam 28 to vary a convergence/divergenceangle of the beam 28. The XY-scan device 60 may be operable to deflectthe beam 28 in two dimensions transverse to the direction of propagationof the beam 28. For example, the XY-scan device 60 can include one ormore mirrors that are controllably deflectable to scan the beam 28 intwo dimensions transverse to the direction of propagation of the beam28. Accordingly, the combination of the z-scan device 58 and the xy-scandevice 60 can be operated to controllably scan the focal point in threedimensions, for example, within the eye of the patient.

As shown further in the illustrated embodiment, a camera 62 andassociated video illumination 64 can be integrated with the scanningassembly 18. The camera 62 and the beam 28 may share a common opticalpath through the objective lens assembly 20 to the eye. A video dichroic66 may be used to combine/separate the beam 28 with/from theillumination wavelengths used by the camera. For example, the beam 28can have a wavelength of about 355 nm and the video illumination 64 canbe configured to emit illumination having wavelengths greater than 450nm. Accordingly, the video dichroic 66 can be configured to reflect the355 nm wavelength while transmitting wavelengths greater than 450 nm.

As should be appreciated, the laser surgery system 10 scans the eye withfocal points of more than one electromagnetic radiation beam, where theelectromagnetic radiation beams have varying degrees of polarization dueto a varying wave plate orientation. The plurality of scans maycompensate for imaging signal loss due to local cornea birefringenceproperties.

The system 10 can include control and conditioning components. Forexample, such control components can include components such as a beamattenuator to control the energy of the laser pulse and the averagepower of the pulse train, a fixed aperture to control thecross-sectional spatial extent of the beam containing the laser pulses,one or more power monitors to monitor the flux and repetition rate ofthe beam train and therefore the energy of the laser pulses, and ashutter to allow/block transmission of the laser pulses. Suchconditioning components can include an adjustable zoom assembly to adaptthe beam containing the laser pulses to the characteristics of thesystem 10 and a fixed optical relay to transfer the laser pulses over adistance while accommodating laser pulse beam positional and/ordirectional variability, thereby providing increased tolerance forcomponent variation.

The control electronics 70 controls the operation of and can receiveinput from the laser assembly 12, the confocal detection assembly 14,free-floating mechanism 16, the scanning assembly 18, the objective lensassembly 20, the patient interface 22, control panel/graphical userinterface (GUI) 72, and user interface devices 74 via communicationpaths. The communication paths can be implemented in any suitableconfiguration, including any suitable shared or dedicated communicationpaths between the control electronics 70 and the respective systemcomponents.

The control electronics 70 can include any suitable components, such asone or more processors, one or more field-programmable gate array(FPGA), and one or more memory storage devices. The control electronics70 is operatively coupled via the communication paths with the laserassembly 12, the confocal detection assembly 14, the free-floatingmechanism 16, the scanning assembly 18, the control panel/GUI 72, andthe user interface devices 74. In many embodiments, the controlelectronics 70 controls the control panel/GUI 72 to provide forpre-procedure planning according to user specified treatment parametersas well as to provide user control over the laser eye surgery procedure.

The control electronics 70 can include a processor/controller that isused to perform calculations related to system operation and providecontrol signals to the various system elements. A computer readablemedium can be coupled to the processor in order to store data used bythe processor and other system elements. The processor interacts withthe other components of the system as described more fully throughoutthe present specification. In an embodiment, the memory can include alook up table that can be utilized to control one or more components ofthe laser system surgery system.

The processor can be a general purpose microprocessor configured toexecute instructions and data such as a processor manufactured by theIntel Corporation of Santa Clara, Calif. It can also be an ApplicationSpecific Integrated Circuit (ASIC) that embodies at least part of theinstructions for performing the method according to the embodiments ofthe present disclosure in software, firmware and/or hardware. As anexample, such processors include dedicated circuitry, ASICs,combinatorial logic, other programmable processors, combinationsthereof, and the like.

The memory can be local or distributed as appropriate to the particularapplication. Memory can include a number of memories including a mainrandom access memory (RAM) for storage of instructions and data duringprogram execution and a read only memory (ROM) in which fixedinstructions are stored. Thus, the memory provides persistent(non-volatile) storage for program and data files, and may include ahard disk drive, flash memory, a floppy disk drive along with associatedremovable media, a Compact Disk Read Only Memory (CD-ROM) drive, anoptical drive, removable media cartridges, and other like storage media.

The user interface devices 74 can include any suitable user input/outputdevice suitable to provide user input to the control electronics 70. Forexample, the user interface devices 74 can include devices such as atouch-screen display/input device, a keyboard, a footswitch, a keypad, apatient interface radio frequency identification (RFID) reader, anemergency stop button, a key switch, and so on.

Next, the characteristics of a cataract lens cut by the laser system 10will be discussed. Received light is scattered by the clouding of acataract lens. The higher the grade of the cataract, the more laserenergy is needed to overcome the scattering and attenuation of the lensto deposit the beam energy at a desired location. Similarly, along anincreasing depth of the cataract, the attenuation of beam energy willincrease. For these reasons, a white cataract cannot be laser treated,but a semi-transparent cataract can be laser cut.

Increasing laser energy into a cataract lens may compensate forscattering losses at a given depth, but shallow layers of the lens arethen treated with higher energy levels than desirable. For example, highlaser energy deposition in grade 1-2 cataracts create large bubbles andhigh laser energy deposition in grade 2-4 cataracts propagate cracks inthe lamellas. Therefore, simply increasing the energy level of atreatment beam into a lens will not improve lens fragmentation.

For sub-nanosecond laser systems, a sensitive range of energies areavailable to cut a cataract cleanly without cracking. If the energyapplied is small, incomplete separation of tissue results. If the energyapplied is high, then excess collateral damage in the tissue appears andsubsequent laser pulses scatter due to an irregular refraction indexchange. Furthermore, excessive energy will slow down the fragmentationprocedure due to a maximum safe power of treatment.

The methods and systems described herein improve the consistency andquality of a laser fragmentation cut by adjusting the treatment energyto match the dynamic range of energies needed to form consistent cuts atdifferent depths of the tissue for sub-nanosecond/infrared/picosecondlasers. For instance, some embodiments include an infrared (e.g., 1 μs)laser assembly capable of performing both capsulotomy and lensfragmentation as described in detail below. This configuration furtherprovides a cost-effective and efficient system where a single laserassembly is suitable for a plurality of surgical procedures.

FIG. 3 is a graph illustrating penetration depth versus energy in a lenscut, in accordance with many embodiments. The greater the energy appliedto the tissue, the higher the penetration depth of the cut.Specifically, penetration depth scales linearly with the energy of thebeam.

FIG. 4 is a graph illustrating bubble volume versus cut depth in a lenscut, in accordance with many embodiments. A bubble volume measurementrepresents an intensity of local tissue treatment and it is assumed thatthe energy in the focal spot of a laser pulse is transferred into themechanical energy of the bubble. FIG. 4 illustrates that along a depthof the lens, a bubble volume for a given energy level of a laser pulsedecays exponentially. For a lens cut performed at a single energy, theconsistency of the cut will vary continuously since the bubble volumedecays exponentially. Therefore, maintaining a single energy levelthroughout a depth of the cut provides poor cut quality. The index ofthe exponent is a function of the initial energy. The bubble volume Vmay be expressed by the following equation 1:

$\begin{matrix}{V = {V_{o}{\exp\left\lbrack {- \frac{{xE}_{th}}{x_{o}\left( {E - E_{th}} \right)}} \right\rbrack}}} & \left( {{eq}.\mspace{11mu} 1} \right)\end{matrix}$

Where V_(o) is a bubble coefficient, E_(th) is bubble threshold energy,E is the laser pulse energy, x₀ is penetration depth at 2E_(th), and xis the depth of the cut.

Accordingly, to provide a consistent and uniform laser fragmentation cutalong a depth of a lens, a bubble volume should maintain the same sizethroughout an entire depth of the cut. Setting the bubble volume V as aconstant value const, equation 1 may be reduced to equation 2:

$\begin{matrix}{\frac{{xE}_{th}}{x_{o}\left( {E - E_{th}} \right)} = {const}} & \left( {{eq}.\mspace{11mu} 2} \right)\end{matrix}$

Solving for E provides for equation 3:

$\begin{matrix}{E = {E_{th}\left\lbrack {1 + \frac{x}{{const}\mspace{14mu} x_{o}}} \right\rbrack}} & \left( {{eq}.\mspace{11mu} 3} \right)\end{matrix}$

Typically, the energy threshold E_(th) and depth x are known values. Theenergy E may be preferably selected to be within a range of 2-10 timesthe threshold energy E_(th) to achieve a bubble volume that provides ahigh quality lens cut. In a non-limiting example, if E is set to5E_(th), then const in equation 2 can be solved for. Then substitutingthe solved const into equation 3 results in equation 4:

$\begin{matrix}{E = {E_{th}\left\lbrack {1 + \frac{4x}{x_{o}}} \right\rbrack}} & \left( {{eq}.\mspace{11mu} 4} \right)\end{matrix}$

Equation 4 shows that the energy E of the beam increases linearly withincreasing depth to maintain a uniform bubble volume. Conversely, for alens fragmentation that begins at a bottom of lens, the energy E shoulddecrease linearly as the cut depth decreases to maintain a uniformbubble volume and achieve a high quality cut.

FIG. 5 shows a flowchart of a fragmentation pattern method 500 of alens, in accordance with many embodiments. In the following non-limitingexample, a laser beam trajectory is for lens fragmentation in cataractsurgery. A laser cataract surgery system 10 is provided and includes asub-nanosecond laser assembly 12 generating a treatment beam 28 thatincludes a plurality of laser beam pulses. The sub-nanosecond laserassembly 12 is, for example, a picosecond laser outputting a 150picosecond treatment beam. The method 500 comprises the following mainsteps.

In step 502, the lens fragmentation process begins with reception of aplurality of input parameters. The trajectory may be computed based onfragmentation parameters including grid shape, depth, diameter, limiteddiameter (mm), segmentation/soft grid spacing (μm), diagnostic lensthickness (mm), spot spacing (μm), depth spacing (μm), number of crossreplicates, lens anterior safe distance (μm), iris safe distance (μm),iris angle NA (deg), lens posterior safe distance (μm), pulse energy(μJ), average power (mW), and the like.

Selection of diagnostic thickness allows the user to input a previouslymeasured lens thickness. The diameter parameter may be maximized to thediameter of the lens segmentation or limited so as to constrain thediameter of the lens segmentation. The grid shape parameter allowsselection of quadrant, sextant, and octant cuts, for example. The gridspacing parameter defines the density of the grid. The segmentation/softgrid spacing parameter defines the separation of the grid from thecenter of the fragmentation pattern (e.g., the middle cross). The spotspacing parameter defines the distance between laser burn spots. Lensfragmentation is performed from the posterior to anterior of the lens.Therefore, the pulse energy is selected for the bottom of the cut. Thepulse energy may preferably be selected to be a value between two to tentimes the threshold energy in order to provide a cut without bridging orcracking. For example, the sub-nanosecond laser source may preferablygenerate the treatment beam with an energy five times the energythreshold of the tissue.

In step 504, the processor determines a lens cut fragmentation patternthat defines the laser trajectory of the lens segmentation treatment.The laser trajectory includes a set of positions and correspondingenergies and is based on the received input parameters.

In step 506, the set of energy settings corresponding to the trajectorypositions are determined by the processor. As discussed above, theenergy of the treatment beam is adjusted to match a depth of the cutaccording to the above equations. Specifically, the energy increaseslinearly with increasing depth of the cut. The energies of the treatmentbeam are determined as a linear function of a depth of the lens cutpattern. Since the cut begins from a bottom of the lens, the energy ofthe treatment beam decreases as a function of the depth of the lenslinearly from the posterior to the anterior of the lens. By scaling thetreatment beam energy to a depth of the lens, a consistent bubble volumeis maintained to ensure a high quality cut. Scattering coefficients ateach depth may be extracted from OCT, confocal scanning or video imagesas described above. In step 508, the processor controls the system 10 togenerate and output the treatment beam 28 according to the lasertrajectory and corresponding energy settings to cut the fragmentationpattern into the lens. A treatment beam 28 is generated by thesub-nanosecond laser assembly 12 and includes a plurality of laser beampulses. The treatment beam 28 is output according to the lens cutpattern of step 504 and energies of step 506.

The processor system may comprise tangible medium embodying instructionsof a computer program to perform one or more of the method steps asdescribed herein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. The term “connected” is to beconstrued as partly or wholly contained within, attached to, or joinedtogether, even if there is something intervening. Recitation of rangesof values herein are merely intended to serve as a shorthand method ofreferring individually to each separate value falling within the range,unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described herein can be performed in any suitableorder unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or exemplarylanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate embodiments of the invention and does not pose a limitationon the scope of the invention unless otherwise claimed. No language inthe specification should be construed as indicating any non-claimedelement as essential to the practice of the invention.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

What is claimed is:
 1. A laser cataract surgery system, comprising: asub-nanosecond laser source generating a treatment beam that includes aplurality of laser beam pulses; an optical delivery system coupled tothe sub-nanosecond laser source to receive and direct the treatmentbeam; and, a processor coupled to the sub-nanosecond laser source andthe optical delivery system, the processor comprising a tangiblenon-volatile computer readable medium comprising instructions to:determine a lens cut pattern for lens fragmentation, the lens cutpattern being defined inside a lens of an eye; determine a plurality ofenergies of the treatment beam as a linear function of a depth of thelens cut pattern to generate bubbles of a constant bubble volume atdifferent depths, the depth for each given location of the lens cutpattern being a distance from an anterior surface of the lens to thegiven location inside the lens; and output the treatment beam accordingto the lens cut pattern and the determined energies.
 2. The lasercataract system of claim 1, wherein the plurality of energies of thetreatment beam are between twice an energy threshold and ten times anenergy threshold.
 3. The laser cataract system of claim 2, wherein theenergy threshold is an energy level at which visible damage in tissue isfirst observed.
 4. The laser cataract system of claim 3, wherein thesub-nanosecond laser source generates the treatment beam with an energyfive times the energy threshold of the tissue.
 5. The laser cataractsystem of claim 1, wherein the sub-nanosecond laser source is apicosecond laser.
 6. The laser cataract system of claim 1, wherein thesub-nanosecond laser generates a 150 picosecond treatment beam.
 7. Thelaser cataract system of claim 1, further comprising: an image capturesystem for capturing an image of the eye.
 8. The laser cataract systemof claim 1, further comprising: a patient interface system to couple theeye with the optical delivery system so as to constrain the eye relativeto the optical delivery system.
 9. A method of fragmenting a lens of aneye, comprising: generating a treatment beam that includes a pluralityof laser beam pulses by a sub-nanosecond laser source; determining alens cut pattern for lens fragmentation, the lens cut pattern beingdefined inside the lens; determining a plurality of energies of thetreatment beam as a linear function of a depth of the lens cut patternto generate bubbles of a constant bubble volume at different depths, thedepth for each given location of the lens cut pattern being a distancefrom an anterior surface of the lens to the given location inside thelens; and outputting the treatment beam according to the lens cutpattern and the determined energies.
 10. The method of claim 9, whereinthe plurality of energies of the treatment beam are between twice anenergy threshold and ten times an energy threshold.
 11. The method ofclaim 10, wherein the energy threshold is an energy level at whichvisible damage in tissue is first observed.
 12. The method of claim 11,wherein the sub-nanosecond laser source generates the treatment beamwith an energy five times the energy threshold of the tissue.
 13. Themethod of claim 9, wherein the sub-nanosecond laser source is apicosecond laser.
 14. The method of claim 9, wherein the sub-nanosecondlaser generates a 150 picosecond treatment beam.
 15. The method of claim9, further comprising: capturing an image of the eye by an image capturesystem.
 16. The method of claim 9, further comprising: coupling the eyewith the optical delivery system so as to constrain the eye relative tothe optical delivery system by a patient interface system.
 17. A lasercataract surgery system, comprising: a sub-nanosecond laser sourcegenerating a treatment beam that includes a plurality of laser beampulses; an optical delivery system coupled to the sub-nanosecond lasersource to receive and direct the treatment beam; and, a processorcoupled to the sub-nanosecond laser source and the optical deliverysystem, the processor comprising a tangible non-volatile computerreadable medium comprising instructions to: determine a lens cut patterninside a lens of an eye from a posterior to an anterior of the lens forlens fragmentation; scale a plurality of energies of the treatment beamas a linear function of a depth of the lens cut pattern to maintain aconstant bubble volume formed by the treatment beam at different depths,the depth for each given location of the lens cut pattern being adistance from an anterior surface of the lens to the given locationinside the lens; and output the treatment beam according to the lens cutpattern and the determined energies.
 18. The laser cataract system ofclaim 17, wherein the energy of the treatment beam decreases linearly asa function of the depth of the lens from the posterior to the anteriorof the lens.
 19. The laser cataract system of claim 17, wherein theenergy of the treatment beam at the posterior of the lens is betweentwice an energy threshold and ten times an energy threshold, wherein theenergy threshold is an energy level at which visible damage in tissue isfirst observed.